<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <title>效率测试</title>
</head>

<body>

</body>
<script>
    function fn() {
        var d1 = +new Date();
        var array = [];
        for (let i = 0; i < 1000; i++) {
            array.push('<div style="width:100px; height:2px; border:1px solid blue;"></div>');
        }
        document.body.innerHTML = array.join('');
        var d2 = +new Date();
        console.log(d2 - d1);
    }
    fn();
</script>

</html>